The development of security systems is becoming more of an important issue with regard to the safety and security of people. As an example, with the increased need for security in large public venues such as airports and stadiums, the implementation of security systems is becoming more prevalent. A number of security systems exist for the detection of contraband on a person, such as walk-through metal detectors and wands. However, such systems are typically limited in that they are capable only of detecting metal, and often only certain types of metals. Furthermore, it is not necessarily just people that need to be monitored for security purposes, but also the personal belongings of people. For example, people often bring carry-on items onto an airplane when they fly. While it is important to screen such carry-on items, such screening must be weighed against a competing concern with efficiency of security monitoring and the impingement of personal freedoms.
There are a variety of security measures in place to screen personal items. Some of them are large, complicated, and expensive, such as conveyor-belt fed X-ray machines that are typically employed in airports. Some measures are very simple, such as security personnel searching personal bags upon entering stadiums and festivals. However, all such systems can be easily spoofed by hiding contraband items in locations that appear to be obvious as something else, particularly in light of efficient security monitoring. For example, security personnel are unlikely to search what appears to be a typical twenty-ounce plastic bottle of soda because it would be inefficient and because people would be unhappy to have their drink poured out. However, a clever criminal could have hidden drugs, ammunition, or explosives in a recess behind the label, with real soda above and below the recess so as to make it look like a full bottle of soda. As another example, the bottle may appear to contain soda, whereas the liquid inside may not actually be soda, or may be soda that includes alcohol, such that it is smuggled into an area where alcohol is prohibited. Therefore, existing security screening measures may be insufficient to provide adequate public safety.